Hybrid powertrain with a gearbox and method to control the hybrid powertrain

ABSTRACT

A hybrid powertrain that includes a combustion engine (4) and a gearbox (2) with an input shaft (8) and an output shaft (20); a first planetary gear (10) connected to the input shaft (8); a second planetary gear (12) connected to the first planetary gear (10); a first electrical machine (14) connected to the first planetary gear (10); a second electrical machine (16) connected to the second planetary gear (12); at least one gear pair (G1, 60, 72) connected to the first planetary gear (10) and to the output shaft (20); and at least one gear pair (G2, 66, 78) connected to the second planetary gear (12) and to the output shaft (20), a countershaft (18) provided between the combustion engine (4) and the gearbox (2) so that the engine (4) can be disconnected from the gearbox (2). Also disclosed is a method for controlling the disclosed hybrid powertrain (3). Also a vehicle (1) includes such a gearbox (2), and a method to control such a gearbox (2). Also a computer program (P) to control a gearbox.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 14/780,472, filed Sep.25, 2015, which is a 35 U.S.C. § 371 national phase conversion ofPCT/SE2014/050341, filed Mar. 20, 2014, which claims priority to SwedishApplication No. 1350394-1, filed Mar. 27, 2013, Swedish Application No.1350392-5, filed Mar. 27, 2013 and Swedish Application No. 1350393-3,filed Mar. 27, 2013, the contents of which are incorporated herein byreference.

BACKGROUND TO THE INVENTION AND PRIOR ART

The present invention relates to a hybrid powertrain. The inventionrelates also to a vehicle provided with a hybrid powertrain, a methodfor controlling a hybrid powertrain, a computer program to enableperformance of a method for controlling a hybrid powertrain, and acomputer program product comprising a computer readable medium havingstored therein program code to enable the performance of the method by acomputer Other features and advantages of the present invention willbecome apparent from the following description of the invention whichrefers to the accompanying drawings.

Hybrid vehicles may be powered by a primary drive means which may be acombustion engine, and by a secondary drive means which may be anelectrical machine. The electrical machine will be equipped with atleast one energy store, e.g. an electrochemical store for electricalenergy, and with regulating equipment to regulate the flow of electricalenergy between the energy store and the electrical machine. Theelectrical machine may thus serve alternately as a motor and agenerator, depending on the vehicle's operating state. When the vehicleis braked, the electrical machine will generate electrical energy whichgoes into the energy store. This is usually called regenerative brakingwhereby the vehicle is braked by the electrical machine and thecombustion engine. The stored electrical energy will subsequently beused for operation of the vehicle.

A planetary gear usually comprises three components arranged forrotation relative to one another, via a sunwheel, a planet wheel carrierand a ring gear. Knowing the number of teeth which the sunwheel and thering gear have makes it possible to determine the mutual rotation speedsof the three components during operation. One of the planetary gear'scomponents may be connected to an output shaft of a combustion engine.This component of the planetary gear will therefore rotate at a speedcorresponding to that of the engine output shaft. A second component ofthe planetary gear may be connected to an input shaft of a gearbox. Thiscomponent of the planetary gear will therefore rotate at the same speedas the gearbox input shaft. A third component of the planetary gear isconnected to a rotor of an electrical machine to achieve hybridoperation. This component of the planetary gear will therefore rotate atthe same speed as the electrical machine's rotor if they are connecteddirectly to one another. Alternatively, the electrical machine may beconnected to the third component of the planetary gear via atransmission which has a gear ratio, in which case they may rotate atdifferent speeds. The speed and/or the torque of electrical machines maybe regulated steplessly. In operating situations where a desired speedand/or torque are to be imparted to the gearbox input shaft, a controlunit will use knowledge of the combustion engine's speed to calculatethe speed at which the third component needs to be driven to cause thegearbox input shaft to rotate at the desired speed. A control unit willactivate the electrical machine to impart the calculated speed to thethird component and hence the desired speed to the gearbox input shaft.

During acceleration of the vehicle an increased torque has to bedelivered from the combustion engine and the electrical machine to thegearbox and thence to the vehicle's tractive wheels. As both thecombustion engine and the electrical machine are connected to theplanetary gear, the largest possible torque delivered by them will belimited by whichever of their greatest torques is less than that of theother, taking into account the gear ratio between them. In situationswhere the greatest torque of the electrical machine is less than thegreatest torque of the combustion engine, taking into account the gearratio between them, the electrical machine will not be able to generatesufficient reaction torque to the planetary gear, with the result thatthe combustion engine will not be able to transmit its greatest torqueto the gearbox and thence to the vehicle's tractive wheels. The greatesttorque transferrable to the gearbox is thus limited by the capacity ofthe electrical machine. This is also indicated by the so-called planetequation.

The space available for the propulsion device in a vehicle is oftenlimited. If the propulsion device comprises a plurality of components(e.g. a combustion engine, an electrical machine, a gearbox and aplanetary gear) the configuration needs to be compact. If furthercomponents (e.g. a regenerative brake device) are to be incorporated,the need for a compact configuration of the components of the propulsiondevice will be still greater. At the same time, the dimensions of thesecomponents have to enable them to absorb necessary forces and torques.

Certain types of vehicles, particularly heavy trucks and buses, need alarge number of gearsteps. This increases the number of components inthe gearbox, which has to be dimensioned to absorb large forces andtorques that occur in such heavy vehicles, thereby increasing its sizeand weight.

The components of the propulsion device are also required to be of highreliability and high operational safety. A gearbox that comprises discclutches is subject to wear which affects its reliability and servicelife.

During regenerative braking, kinetic energy is converted to electricalenergy which goes into an energy store, e.g. accumulators. A factorwhich affects the service life of the energy store is its number ofcycles of supplying current to and absorbing current from the electricalmachines. The more numerous the cycles, the shorter the energy store'sservice life.

In certain operating conditions it is desirable to switch the combustionengine off with the object of saving fuel and with a view to preventingcooling of its exhaust post-treatment system. When the hybrid powertrainis part of a vehicle, the vehicle will be driven by the electricalmachines. In a hybrid powertrain, problems may arise if the electricalmachines alone are activated. If the crankshaft of the combustion engineis driven by the electrical machines without the engine being activated,excessive wear of the engine's bearings may occur.

EP-B1-1126987 discloses a gearbox with dual planetary gears. Thesunwheel of each planetary gear is connected to an electrical machineand the ring gears of the planetary gears are connected to one another.The planet wheel carriers of each planetary gear are connected to anumber of pairs of gears in such a way as to provide an infinite numberof gearsteps. Another specification, EP-B1-1280677, also discloses howthe planetary gears may be bridged by a gearstep provided on the outputshaft of the combustion engine.

US-A1-20050227803 discloses a vehicle transmission with two electricalmachines which are connected to respective sunwheels of two planetarygears. The planetary gears have a common planet wheel carrier connectedto the input shaft of the transmission.

WO2008/046185-A1 discloses a hybrid transmission with two planetarygears whereby an electrical machine is connected to one of the planetarygears and a double clutch cooperates with the other planetary gear. Thetwo planetary gears also cooperate with one another via a gearwheeltransmission.

SUMMARY OF THE INVENTION

Despite known solutions in this field, there is a need to furtherdevelop a hybrid powertrain and a method for controlling such a hybridpowertrain in order to optimize the fuel consumption of the hybridpowertrain. There is in particular a need to further develop a hybridpowertrain and a method for controlling it which makes electric drivepossible in a simple way.

The object of the invention is to propose a novel and advantageoushybrid powertrain which makes electric drive possible in a simple way.

Another object of the invention is to propose a novel and advantageousmethod for controlling a hybrid powertrain.

A further object of the invention is to propose a novel and advantageouscomputer program for controlling a hybrid powertrain.

These objects are achieved with the claimed hybrid powertrain.

These objects are also achieved with the claimed vehicle.

These objects are also achieved with the claimed method.

These objects are also achieved with a computer program for controllingthe claimed hybrid powertrain.

These objects are also achieved with a computer program product forcontrolling the claimed hybrid powertrain.

The hybrid powertrain according to the present invention comprises agearbox and a combustion engine connected to the gearbox. The gearboxitself comprises an input and an output shaft, a first planetary gearconnected to the input shaft, a second planetary gear connected to thefirst planetary gear, a first electrical machine connected to the firstplanetary gear, a second electrical machine connected to the secondplanetary gear, at least one gear pair connected to the first planetarygear and to the output shaft and at least one gear pair connected to thesecond planetary gear and to the output shaft. The hybrid powertrainprovided with a clutch device situated between the combustion engine andthe gearbox makes it possible for the combustion engine to bedisconnected from the gearbox and for the hybrid powertrain to be drivenelectrically by the first and the second electrical machine.

The combustion engine may be disconnected with the object of saving fuelor to prevent cooling of its exhaust post-treatment system. It isimportant that the engine output shaft be as motionless as possibleduring electric drive. If torque is transferred to the engine when it isswitched off, there is risk of its shafts moving against bearings withno oil supply, potentially causing destruction of the bearings.According to the present invention, the engine output shaft is allowedto be motionless by the clutch device being situated between it and thegearbox. Thus, when the clutch device is open, the engine will bedisconnected from the gearbox, and when the clutch device is closed, theengine will be connected to the gearbox.

During electric drive there is less need for gear changes in that thefirst and second electrical machines each have a larger speed rangewithin which they work more efficiently than the combustion engine. Bothof the electrical machines are preferably used to propel the vehicleduring electric drive, resulting in a large number of possiblecombinations of different gearsteps.

Changing gear during electric drive always entails the torquecontribution from one electrical machine having to be reduced duringchanges in order to be able to connect/disconnect any desired gear pairto/from a countershaft connected to the output shaft and thereby engagea gear.

The first planetary gear comprises with advantage a first planet wheelcarrier connected to a second sunwheel of the second planetary gear. Inaddition, a first sunwheel of the first planetary gear is firmlyconnected to a first mainshaft, and a second planet wheel carrier of thesecond planetary gear is firmly connected to a second mainshaft. Thefirst planet wheel carrier is preferably connected to the gearbox inputshaft.

Advantageously, the clutch device is situated between the engine outputshaft and the first planetary gear. Advantageously, the clutch device issituated between the engine output shaft and the first planet wheelcarrier. The clutch device is preferably situated between the engineoutput shaft and the gearbox input shaft.

The gearbox is preferably provided with a number of gear pairs thatcomprise gearwheels which can be mechanically locked to and disconnectedfrom a countershaft, resulting in a number of fixed gearsteps that canbe changed without torque breaks. The gearwheels lockable to thecountershaft also result in a compact configuration with highreliability and high operational safety. Alternatively, pinions whichform part of gear pairs may be arranged to be lockable to anddisconnectable from the first or the second mainshaft.

The gear pairs will each have a gear ratio adapted to the vehicle'sdesired operating characteristics. Advantageously, the gear pair withthe highest ratio relative to the other pairs will be connected when thelowest gear is engaged.

Advantageously, a countershaft situated between the respective first andsecond planetary gears and the output shaft is connected to at least onegear pair connected to the first planetary gear and the at least onegear pair connected to the second planetary gear. Advantageously, thecountershaft is connected to the output shaft via a fifth gear pair. Thefact that the at least one gear pair connected to the first planetarygear and the at least one gear pair connected to the second planetarygear are connected to the countershaft may mean that these gear pairsare arranged to be lockable to and disconnectable from the countershaft.An alternative is that the at least one gear pair connected to the firstplanetary gear be arranged to be lockable to and disconnectable from thefirst mainshaft and that the at least one gear pair connected to thesecond planetary gear be arranged to be lockable to and disconnectablefrom the second mainshaft.

Advantageously, a clutch mechanism is provided between the firstmainshaft and the output shaft.

Providing the gearbox, which comprises two planetary gears connected toone another, with a shift element situated between a countershaft andthe gearbox output shaft results in a number of gearsteps whereby torquefrom one planetary gear may be transferred to the countershaft andthence to a mainshaft connected to the second planetary gear in order tofinally transfer torque to the gearbox output shaft.

The electrical machines connected to the planetary gears may generatecurrent and/or impart torque, depending on the desired operating states.In certain operating situations, they may also provide each other withcurrent.

In one embodiment the hybrid powertrain is provided with a number ofgear pairs comprising gearwheels, which are lockable mechanically to thecountershaft and also result in a compact configuration with highreliability and high operational safety.

In one embodiment, a first clutch unit and a second clutch unit areprovided between the planet wheel carrier and the sunwheel of eachplanetary gear. The purpose of these clutch units is to lock each planetwheel carrier to the respective sunwheel. When the planet wheel carrierand the sunwheel are connected to one another, the power from thecombustion engine will pass through the planet wheel carrier, the clutchunit, the sunwheel and thence to the gearbox, with the result that theplanet wheels absorb no torque. This makes it possible for thedimensions of the planet wheels to be appropriate solely to theelectrical machine's torque instead of the combustion engine's torque,making it possible for these wheels to be of smaller dimensions. Theresult is a propulsion device according to the invention which is ofcompact configuration, low weight and low manufacturing cost.

The clutch units and the locking mechanisms preferably comprise anannular sleeve which is moved axially between connected and disconnectedpositions. The sleeve surrounds the rotating components of the gearboxsubstantially concentrically and is moved between the connected anddisconnected positions by a power element. The result is a compactconfiguration with low weight and low manufacturing cost.

A method for controlling the hybrid powertrain preferably comprises thesteps of causing the combustion engine to be disconnected by a clutchdevice; disconnecting rotatable components of the second planetary gearfrom one another; connecting the gear pair which is connected to thefirst planetary gear; disconnecting the gear pair which is connected tothe second planetary gear; and connecting two rotatable components ofthe second planetary gear to one another.

A method for controlling the hybrid powertrain preferably comprises thesteps of causing the combustion engine to be disconnected by a clutchdevice; disconnecting rotatable components of the first planetary gearfrom one another; connecting a gear pair which is connected to thesecond planetary gear; disconnecting a gear pair which is connected tothe first planetary gear; and connecting two rotatable components of thefirst planetary gear to one another.

To be able to disconnect a planetary gear's planet wheel carrier andsunwheel from one another, the hybrid powertrain is controlled in such away that torque balance occurs in the planetary gear. Torque balancemeans a state in which a ring gear that is part of the respectiveplanetary gear is acted upon by a torque which corresponds to theproduct of the torque acting upon the planetary gear's planet wheelcarrier and the gear ratio of the planetary gear while at the same timethe planetary gear's sunwheel is acted upon by a torque corresponding tothe product of the torque acting upon the planet wheel carrier and thegear ratio of the planetary gear. In the situation where two of theplanetary gear's constituent parts (sunwheel, ring gear and planet wheelcarrier) are connected together by a clutch unit, the clutch unit willtransfer no torque between the planetary gear's parts when there istorque balance. The clutch unit may thus easily be moved and theplanetary gear's constituent parts be disconnected.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below by way ofexamples with reference to the attached drawings, in which

FIG. 1 depicts schematically a vehicle in side view with a hybridpowertrain according to the present invention,

FIG. 2 is a schematic sideview of a hybrid powertrain with a gearboxaccording to the present invention,

FIG. 3 is a simplified schematic view of the hybrid powertrain in FIG.2,

FIG. 4 is a flowchart of a method for controlling a hybrid powertrainaccording to the present invention, and

FIG. 5 is a flowchart of a method for controlling a hybrid powertrainaccording to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 is a schematic sideview of a vehicle 1 provided with a gearbox 2and a combustion engine 4 which form part of a hybrid powertrain 3. Theengine 4 is connected to the gearbox 2 which is itself further connectedto the vehicle's tractive wheels 6 via a propeller shaft 9. The tractivewheels are provided with brake devices 7 for braking the vehicle.

FIG. 2 is a schematic sideview of a hybrid powertrain 3 with a gearbox2, which comprises an input shaft 8, respective first and secondplanetary gears 10 and 12, respective first and second electricalmachines 14 and 16, a countershaft 18 and an output shaft 20. The firstplanetary gear 10 has a first ring gear 22 to which a first rotor 24 ofthe first electrical machine 14 is connected. The first planetary gearhas also a first sunwheel 26. The second planetary gear 12 has a secondring gear 28 to which a second rotor 30 of the second electrical machine16 is connected. The second planetary gear has a second sunwheel 32. Thefirst and second sunwheels 26 and 32 are arranged coaxially, which inthe version depicted causes a first mainshaft 34 attached to the firstsunwheel 26 to extend within a second mainshaft 36 which is attached tothe second sunwheel 32 and is provided with a central bore 38. It isalso possible for the first mainshaft 34 to be arranged parallel withand alongside the second mainshaft 36.

The first electrical machine 14 is provided with a first stator 40connected to the vehicle via a gear housing 42 which surrounds thegearbox 2. The second electrical machine 16 is provided with a secondstator 44 connected to the vehicle via the gear housing 42 whichsurrounds the gearbox. The respective first and second electricalmachines 14 and 16 are connected to an energy store 46, e.g. a battery,which energises them in certain operating states of the vehicle. Inother operating states, the electrical machines may serve as generators,in which case current will be supplied to the energy store. Anelectronic control unit 48 is connected to the energy store and controlsthe supply of current to the electrical machines. The energy store ispreferably connected to the electrical machines via a changeover switch49 which is connected to the control unit 48. In certain operatingsituations the electrical machines may also drive one another, in whichcase electrical energy passes from one to the other via the changeoverswitch connected to them. This makes it possible to achieve a powerbalance between the electrical machines. Another computer 53 may also beconnected to the control unit 48 and the gearbox 2.

The first planetary gear 10 is provided with a first planet wheelcarrier 50, which supports a first set of planet wheels 52. The secondplanetary gear 12 is provided with a second planet wheel carrier 51,which supports a second set of planet wheels 54. The first set of planetwheels 52 cooperates with the first ring gear 22 and the first sunwheel26. The second set of planet wheels 54 cooperates with the second ringgear 28 and the second sunwheel 32. The gearbox input shaft 8 isconnected to the first planet wheel carrier 50. The combustion engine 4is connected to the gearbox 2 by a clutch device 106 situated betweenthe engine output shaft 97 and the gearbox input shaft 8. The clutchdevice may be opened to disconnect the combustion engine from the clutchdevice and thereby enable the vehicle to be driven electrically by thetwo electrical machines. The clutch device may take the form of splinedportions which cooperate with a shift sleeve. It may alternatively takethe form of a friction clutch.

A first clutch unit 56 is provided between the first sunwheel 26 and thefirst planet wheel carrier 50. Applying the first clutch unit so thatthe first sunwheel 26 and the first planet wheel carrier are connectedtogether and therefore cannot rotate relative to one another will causethem to rotate at the same speed.

A second clutch unit 58 is provided between the second sunwheel 32 andthe second planet wheel carrier 51. Applying the second clutch unit sothat the second sunwheel and the second planet wheel carrier areconnected together and therefore cannot rotate relative to one anotherwill cause them rotate at the same speed.

The first and second clutch units 56, 58 preferably have respectivefirst and second splined shift sleeves 55 and 57 which are movableaxially relative to a splined portion of the respective first and secondplanet wheel carriers 50 and 51 and relative to a splined portion of therespective sunwheels 26 and 32. Moving the respective shift sleeves 55,57 so that the splined portions are connected via them will respectivelycause the first planet wheel carrier 50 and the first sunwheel 26, andthe second planet wheel carrier 51 and the second sunwheel 32, to becomelocked together and unable to rotate relative to one another.

In the version depicted in FIG. 2, the first clutch unit 56 is situatedbetween the first sunwheel 26 and the first planet wheel carrier 50, andthe second clutch unit 58 is situated between the second sunwheel 28 andthe second planet wheel carrier 51. It is possible, however, for thereto be a further or alternative clutch unit (not depicted) between thefirst ring gear 22 and the first planet wheel carrier 50, and also forthere to be a further or alternative clutch unit (not depicted) betweenthe second ring gear 28 and the second planet wheel carrier 51.

A transmission device 19 comprising a first gear pair 60 situatedbetween the first planetary gear 10 and the output shaft 20 is connectedto the first and the second mainshafts 34, 36. The first gear pair 60comprises a first pinion 62 and a first gearwheel 64 in engagement withone another. A second gear pair 66 situated between the second planetarygear 12 and the output shaft 20 comprises a second pinion 68 and asecond gearwheel 70 in mutual engagement. A third gear pair 72 situatedbetween the first planetary gear 10 and the output shaft 20 comprises athird pinion 74 and a third gearwheel 76 in mutual engagement. A fourthgear pair 78 situated between the second planetary gear 12 and theoutput shaft 20 comprises a fourth pinion 80 and a fourth gearwheel 82in mutual engagement.

The respective first and third pinions 62 and 74 are situated on andfirmly connected to the first mainshaft 34 so that they cannot rotaterelative to it. The respective second and fourth pinions 68 and 80 aresituated on and firmly connected to the second mainshaft 36 so that theycannot rotate relative to it.

The countershaft 18 extends substantially parallel with the first andsecond mainshafts 34 and 36. The first, second, third and fourthgearwheels 64, 70, 76 and 82 are supported by the countershaft. Thefirst pinion 62 engages with the first gearwheel 64, the second pinion68 with the second gearwheel 70, the third pinion 74 with the thirdgearwheel 76, and the fourth pinion 80 with the fourth gearwheel 82.

The first, second, third and fourth gearwheels 64, 70, 76 and 82 canindividually be locked to and disconnected from the countershaft 18 byrespective first, second, third and fourth clutch elements 84, 86, 88and 90. These clutch elements preferably take the form of splinedportions formed on the respective gearwheels 64, 70, 76 and 82 and onthe countershaft and cooperating with fifth and sixth shift sleeves 83,85, which engage mechanically with the splined portions of the first tofourth gearwheels 64, 70, 76 and 82 and the countershaft 18. The firstand third clutch elements 84, 88 are preferably provided with a commonshift sleeve 83, and the second and fourth clutch elements 86, 90 arepreferably provided with a common shift sleeve 85. In the disconnectedstate, relative rotation may occur between the respective gearwheels 64,70, 76 and 82 and the countershaft 18. The clutch elements 84, 86, 88and 90 may also take the form of friction clutches. The countershaft 18bears also a fifth gearwheel 92 which engages with a sixth gearwheel 94situated on the gearbox output shaft 20.

The countershaft 18 is situated between the respective first and thesecond planetary gears 10, 12 and the output shaft 20 in such a way thatit is connected to the output shaft via a fifth gear pair 21, whichcomprises the fifth and sixth gearwheels 92, 94. The fifth gearwheel 92is arranged to be connectable to and disconnectable from thecountershaft by a fifth clutch element 93.

By disconnecting the fifth gearwheel 92 which is situated disconnectablyon the countershaft 18 it is possible to transfer torque from the secondplanetary gear 12 to the countershaft 18, e.g. via the second gear pair66, and to further transfer torque from the countershaft 18 to theoutput shaft 20, e.g. via the first gear pair 60. The result is a numberof gearsteps whereby torque from either of the planetary gears 10, 12may be transferred to the countershaft 18 and thence to whichevermainshaft 34, 36 is connected to the other planetary gear 10, 12, inorder finally to transfer torque to the gearbox output shaft 20. Thisdoes, however, presuppose that a clutch mechanism 96 situated betweenthe first mainshaft 34 and the output shaft 20 is connected, asdescribed in more detail below.

The fifth gearwheel 92 may be locked to and disconnected from thecountershaft 18 by a fifth clutch element 93. The clutch element 93preferably takes the form of splined portions formed on the fifthgearwheel 92 and on the countershaft 18 and cooperating with a ninthshift sleeve 87, which engages mechanically with the splined portions ofthe fifth gearwheel 92 and of the countershaft 18. In the disconnectedstate, relative rotation may occur between the fifth gearwheel 92 andthe countershaft 18. The fifth clutch element 93 may also take the formof friction clutches.

Torque transfer from the gearbox input shaft 8 to the gearbox outputshaft 20 may take place via the respective first or second planetarygear 10 or 12 and the countershaft 18. It may also take place directlyvia the first planetary gear 10, which has its first sunwheel 26connected via the first mainshaft 34 to the gearbox output shaft 20 viaa clutch mechanism 96. The clutch mechanism 96 comprises preferably asplined seventh shift sleeve 100 which is movable axially on the splinedportions of the first mainshaft 34 and of the output shaft 20. Movingthe seventh shift sleeve 100 so that the splined portions connect via itwill lock the first mainshaft 34 to the output shaft 20, which willtherefore both rotate at the same speed. By disconnecting the fifthgearwheel 92 of the fifth gear pair 21 from the countershaft 18 it ispossible for torque from the second planetary gear 12 to be transferredto the countershaft 18 and thence to the first mainshaft 34 connected tothe first planetary gear 10 in order, via the clutch mechanism 96, tofinally transfer torque to the gearbox output shaft 20.

During operation, the gearbox 2 may in certain situations operate insuch a way that one of the sunwheels 26 and 32 is locked to therespective first or second planet wheel carrier 50 or 51 by therespective first or second clutch unit 56 or 58. The respective first orsecond mainshaft 34 or 36 will then rotate at the same speed as thegearbox input shaft 8, depending on which of the sunwheels 26 and 32 islocked to the respective planet wheel carrier. One or both of theelectrical machines 14 and 16 may serve as generators to supplyelectrical energy to the energy store 46. Alternatively, the respectiveelectrical machine may provide a torque contribution to increase thetorque on the output shaft 20. In certain operating situations theelectrical machines will provide each other with electrical energyindependently of the energy store 46.

It is also possible for both of the electrical machines 14 and 16 tosimultaneously generate current to the energy store 46. During enginebraking, the driver releases the vehicle's accelerator pedal (notdepicted). The gearbox output shaft 20 then drives one or both of theelectrical machines 14, 16 while at the same time the combustion engine4 and the electrical machines 14, 16 apply engine braking. Theelectrical machines 14, 16 here generate electrical energy which goesinto the vehicle's energy store 46. This operating state is calledregenerative braking. The engine output shaft 97 is disconnected so asto become independent of the engine's idling speed during braking. Thismeans that one or both of the electrical machines 14 and 16 will serveas brakes and generate electrical energy which goes into the energystore 46.

The control unit 48 is connected to the electrical machines 14 and 16and adapted to causing them in certain appropriate operating situationsto use stored electrical energy for imparting driving force to thegearbox output shaft 20, and in other operating situations to use thekinetic energy of the gearbox output shaft 20 to gain and storeelectrical energy. The control unit 48 therefore monitors the speedand/or torque of the engine output shaft 97 via sensors 98 associatedwith the electrical machines 14, 16, and the speed and/or torque of thegearbox output shaft 20, in order thereby to obtain information andcause the electrical machines 14, 16 to serve as electric motors orgenerators. The control unit 48 may be a computer with suitable softwarefor this purpose. It will also control the flow of electrical energybetween the energy store 46 and the respective stators 40 and 44 of theelectrical machines 14, 16. In situations where the electrical machines14, 16 serve as motors, stored electrical energy is supplied from theenergy store 46 to the stators. In situations where the electricalmachines 14, 16 serve as generators, electrical energy is supplied fromthe stators to the energy store 46. As mentioned above, however, theelectrical machines 14, 16 may in certain operating situations provideeach other with electrical energy independently of the energy store 46.

The first and second clutch units 56 and 58, the first, second, third,fourth and fifth clutch elements 84, 86, 88, 90 and 93, the clutchmechanism 96 between the first mainshaft 34 and the output shaft 20, andthe locking device 102 between the first planet wheel carrier 50 and thegear housing 42, are connected to the control unit 48 via theirrespective shift sleeves, which are preferably activated and deactivatedby electrical signals from the control unit 48. The shift sleeves arepreferably moved by undepicted power means, e.g. by hydraulic orpneumatic cylinders. It is also possible for them to be moved byelectrically operated power means.

In the example depicted in FIG. 2 there are four pinions 62, 68, 74 and80, four gearwheels 64, 70, 76 and 82 and two planetary gears 10 and 12with associated electrical machines 14 and 16. It is possible, however,for the gearbox to be provided with more or fewer pinions and gearwheelsand with more planetary gears with associated electrical machines.

As described above, torque from the gearbox 2 is extracted from theoutput shaft 20. It is also possible for it to be extracted directlyfrom the first or the second mainshaft 34, 36 or directly from thecountershaft 18. It may also be extracted in parallel from two or allthree of the shafts 18, 34, 36 at the same time.

A shift from a first gear to a sixth gear is described below in a casewhere the hybrid powertrain 3 is part of a vehicle 1. The first planetwheel carrier 50 and the first sunwheel 26 are connected together by thefirst clutch unit 56. In addition, the second planet wheel carrier 51and the second sunwheel 32 are connected together by the second clutchunit 58. The clutch unit 106 is open and the combustion engine 4 istherefore disconnected and the vehicle is propelled by the twoelectrical machines 14, 16.

In a first gear, the gear pairs 60, 72 connected to the first planetarygear 10 are disconnected from the countershaft 18 while at the same timethe fourth gear pair 78 is connected to the countershaft 18. Thus thefourth gearwheel 82 is connected to the countershaft 18 by the fourthclutch element 90. The fifth gear pair 21 is connected to thecountershaft 18.

The first, second, third and fourth gear pairs 60, 66, 72, 78 each havea ratio appropriate to the vehicle's desired operating characteristics.In the embodiment example in FIG. 2, the fourth pair 78 has a higherratio than the first, second and third pairs 60, 66, 72, so it will beconnected when the lowest gear is engaged. Like the fourth pair, thesecond gear pair 66 transfers torque between the second mainshaft 36 andthe countershaft 18 and might instead have a higher ratio than the otherpairs 60, 72, 78, in which case it would therefore be connected when thelowest gear is engaged.

To shift to a second gear, the two electrical machines 14, 16 areoperated in such a way that torque balance occurs in the secondplanetary gear 12. Thereafter the second clutch unit 58 is moved so thatthe second planet wheel carrier 51 and the second sunwheel 32 aredisconnected from one another. The first electrical machine 14 is thenoperated in such a way that a synchronous speed is reached between thecountershaft 18 and the first gear pair 60, which means that asynchronous speed occurs between the first gearwheel 64 and thecountershaft 18. Thereafter the first gearwheel 64 is connected to thecountershaft 18 by the first clutch element 84. The two electricalmachines 14, 16 are then operated in such a way that a torque-free stateoccurs between the countershaft 18 and the fourth gearwheel 82, followedby the fourth clutch element 90 being moved so that the fourth gearwheel82 and hence the fourth gear pair 78 are disconnected from thecountershaft 18. Finally, the second electrical machine 16 is operatedin such a way that a synchronous speed is reached in the secondplanetary gear 12, followed by the second planet wheel carrier 52 andthe second sunwheel 32 being connected together by the second clutchunit 58. The vehicle will now be running in a second gear.

To shift from a first to a third gear, the two electrical machines 14,16 are operated in such a way that torque balance occurs in the firstplanetary gear 10. Thereafter the first clutch unit 56 is moved so thatthe first planet wheel carrier 50 and the first sunwheel 26 aredisconnected from one another. The second electrical machine 16 is thenoperated in such a way that a synchronous speed is reached between thecountershaft 18 and the second gear pair 66, which means that asynchronous speed occurs between the second gearwheel 70 and thecountershaft 18. Thereafter the second gearwheel 70 is connected to thecountershaft 18 by the second clutch element 86. The two electricalmachines 14, 16 are then operated in such a way that a torque-free stateoccurs between the countershaft and the first gearwheel 64, followed bythe first clutch element 84 being moved so that the first gearwheel 64and hence the first gear pair 60 are disconnected from the countershaft18. Finally, the first electrical machine 14 is operated in such a waythat a synchronous speed is reached in the first planetary gear 10,followed by the first planet wheel carrier 50 and the first sunwheel 26being connected together by the first clutch unit 56. The vehicle willnow be running in a first gear.

To shift from a third gear to a fourth gear, the two electrical machines14, 16 are operated in such a way that torque balance occurs in thesecond planetary gear 12. Thereafter the second clutch unit 58 is movedso that the second planet wheel carrier 51 and the second sunwheel 32are disconnected from one another. The first electrical machine 14 isthen operated in such a way that a synchronous speed is reached betweenthe countershaft 18 and the third gear pair 72, which means that asynchronous speed occurs between the third gearwheel 76 and thecountershaft 18. Thereafter the third gearwheel 76 is connected to thecountershaft 18 by the third clutch element 88. The two electricalmachines 14, 16 are then operated in such a way that a torque-free stateoccurs between the countershaft 18 and the second gearwheel 70, followedby the second clutch element 86 being moved so that the second gearwheel70 and hence the second gear pair 66 are disconnected from thecountershaft 18. Finally, the second electrical machine 16 is operatedin such a way that a synchronous speed is reached in the secondplanetary gear 12, followed by the second planet wheel carrier 51 andthe second sunwheel 32 being connected together by the second clutchunit 58. The vehicle will now be running in a fourth gear.

To change from a fourth to a sixth gear, the two electrical machines 14,16 are operated in such a way that torque balance occurs in the secondplanetary gear 12. Thereafter the second clutch unit 58 is moved so thatthe second planet wheel carrier 51 and the second sunwheel 32 aredisconnected from one another. Thereafter the second electrical machine16 is operated in such a way that a synchronous speed is reached betweenthe countershaft 18 and the second gear pair 66 or the fourth gear pair78. Thereafter the second gearwheel 70 is connected to the countershaft18 by the second clutch element 86, or the fourth gearwheel 82 isconnected to the countershaft 18 by the fourth clutch element 90.Thereafter the two electrical machines 14, 16 are operated in such a waythat a torque-free state occurs between the countershaft 18 and thethird gearwheel 76, followed by the third clutch element 88 being movedso that the third gearwheel 76 and hence the third gear pair 72 aredisconnected from the countershaft 18. The first electrical machine 14is then operated in such a way that a synchronous speed is reachedbetween the first mainshaft 34 and the output shaft 20, followed by theclutch mechanism 96 being used to connect the first mainshaft 34 to theoutput shaft 20. In addition, the two electrical machines 14, 16 areoperated in such a way that a torque-free state occurs between thecountershaft 18 and the previously connected second or fourth gear pair66, 78, followed by the second or fourth clutch element 86, 90 beingmoved so that the second or fourth gear pair 66, 78 is disconnected fromthe countershaft 18. Thereafter the second electrical machine 16 isoperated in such a way that a torque-free state occurs between the fifthgear pair 21 and the countershaft 18. When a torque-free state isreached, the fifth clutch element 93 is disengaged and the fifth gearpair 21 is disconnected from the countershaft 18. Finally the secondelectrical machine 16 is operated in such a way that a synchronous speedis reached in the second planetary gear 12, followed by the secondplanet wheel carrier 51 and the second sunwheel 32 being connectedtogether by the second clutch unit 58.

FIG. 3 illustrates the hybrid powertrain 3 of FIG. 2 in a simplifiedview in which certain components have been omitted for the sake ofclarity. G1 in FIG. 3 takes the form of at least one gear pair connectedto the first mainshaft 34 and thereby to the first planetary gear 10,and G2 takes the form of at least one gear pair connected to the secondmainshaft 36 and thereby to the second planetary gear 12. These gearpairs G1, G2 are also connected to the output shaft 20 via thecountershaft 18. G1 and G2 may each comprise one or more gear pairs. Thegear pair G1 connected to the first planetary gear 10 may for examplecomprise the first gear pair 60 and/or the third gear pair 72, asdescribed with reference to FIG. 2. The gear pair G2 connected to thesecond planetary gear 12 may for example comprise the second gear pair66 and/or the fourth gear pair 78, as described with reference to FIG.2. Also depicted is at least one gear pair G3 which is connected to theoutput shaft 20 and the countershaft 18 and may take the form of thefifth gear pair 21 described with reference to FIG. 2. G3 may compriseone or more gear pairs.

Embodiments for controlling the hybrid powertrain 3 are described below.The first planet wheel carrier 50 and the first sunwheel 26 areconnected together by the first clutch unit 56. In addition, the secondplanet wheel carrier 51 and the second sunwheel 32 are connectedtogether by the second clutch unit 58. The clutch unit 106 is open, sothe combustion engine is disconnected and the hybrid powertrain isdriven by the two electrical machines. At least one gear pair G3connected to the countershaft 18 and to the output shaft 20 ispreferably connected and locked to the countershaft 18 so that thetorque from the two electrical machines 14, 16 is transferred to theoutput shaft 20 via the countershaft 18 and the gear pair G3.

In one embodiment an upshift from one gear to another is effected by thehybrid powertrain being caused to disconnect the second planet wheelcarrier 51 and the second sunwheel 32. This is achieved by operating thetwo electrical machines in such a way that torque balance occurs in thesecond planetary gear 12. Thereafter the second clutch unit 58 is movedso that the second planet wheel carrier 51 and the second sunwheel 32are disconnected from one another.

In addition, the first electrical machine 14 is operated in such a waythat a synchronous speed is reached between the countershaft 18 and agear pair G1 which is connected to the first planetary gear 10, followedby the gear pair G1 connected to the first planetary gear 10 beingconnected to the countershaft 18. The two electrical machines 14, 16 arethen operated in such a way that a torque-free state occurs between thecountershaft 18 and a gear pair G2 which is connected to the secondplanetary gear 12, followed by the gear pair G2 connected to the secondplanetary gear 12 being disconnected from the countershaft 18.Thereafter the second electrical machine 16 is operated in such a waythat a synchronous speed is reached between the second planet wheelcarrier 51 and the second sunwheel 32, followed by their being connectedtogether by the second clutch unit 58.

In one embodiment an upshift from one gear to another is effected by thehybrid powertrain being further caused to disconnect the first planetwheel carrier 50 and the first sunwheel 26 from one another. This isachieved by the two electrical machines 14, 16 being operated in such away that torque balance occurs in the first planetary gear 10.Thereafter the first clutch unit 56 is moved so that the first planetwheel carrier 50 and the first sunwheel 26 are disconnected from oneanother.

In addition, the second electrical machine 16 is operated in such a waythat a synchronous speed is reached between the countershaft 18 and agear pair G2 which is connected to the second planetary gear 12.Thereafter the gear pair G2 connected to the second planetary gear 12 isconnected to the countershaft 18. The two electrical machines 14, 16 arethen operated in such a way that a torque-free state occurs between thecountershaft 18 and a gear pair G1 which is connected to the firstplanetary gear 10, followed by the gear pair G1 connected to the firstplanetary gear 10 being disconnected from the countershaft 18.Thereafter the first electrical machine 14 is operated in such a waythat a synchronous speed is reached between the first planet wheelcarrier 50 and the first sunwheel 26, followed by their being connectedtogether by the first clutch unit 56.

In a further embodiment, an upshift from one gear to another is effectedby the hybrid powertrain further being caused to disconnect the secondplanet wheel carrier 51 and the second sunwheel 32. This is achieved byoperating the two electrical machines 14, 16 in such a way that torquebalance occurs in the second planetary gear 12. Thereafter the secondclutch unit 58 is moved so that the second planet wheel carrier 51 andthe second sunwheel 32 are disconnected from one another.

Thereafter, the second electrical machine 16 is operated in such a waythat a synchronous speed is reached between the countershaft 18 and agear pair G2 which is connected to the second planetary gear 12.Thereafter the gear pair G2 connected to the second planetary gear 12 isconnected to the countershaft 18. Thereafter the two electrical machines14, 16 are operated in such a way that a torque-free state occursbetween the countershaft 18 and a gear pair G1 which is connected to thefirst planetary gear 10, followed by the gear pair G1 connected to thefirst planetary gear 10 being disconnected from the countershaft 18. Thefirst electrical machine 14 is then operated in such a way that asynchronous speed is reached between the first mainshaft 34 and theoutput shaft 20, followed by the clutch mechanism 96 being used toconnect these two shafts together. In addition, the two electricalmachines 14, 16 are operated in such a way that a torque-free stateoccurs between the countershaft 18 and the previously connected gearpair G2 which is connected to the second planetary gear 12, followed bythe gear pair G2 connected to the second planetary gear 12 beingdisconnected from the countershaft 18. The second electrical machine 16is thereafter operated in such a way that a torque-free state occursbetween the countershaft 18 and the gear pair G3 which is connected tothe countershaft 18 and to the output shaft 20. When a torque-free stateis reached, the gear pair G3 connected to the countershaft 18 and to theoutput shaft 20 is disconnected from the countershaft 18. Finally thesecond electrical machine 16 is operated in such a way that asynchronous speed is reached between the second planet wheel carrier 51and the second sunwheel 32, followed by their being connected togetherby the second clutch unit 58.

FIG. 4 is a flowchart of a method for controlling a hybrid powertrain 3during electric drive. The hybrid powertrain comprises a combustionengine 4 and a gearbox 2 which is provided with an input shaft 8 and anoutput shaft 20; a first planetary gear 10 connected to the input shaft8; a second planetary gear 12 connected to the first planetary gear 10;a first electrical machine 14 connected to the first planetary gear 10;a second electrical machine 16 connected to the second planetary gear12; at least one gear pair G1, 60, 72 connected to the first planetarygear 10 and to the output shaft 20, and at least one gear pair G2, 66,78 connected to the second planetary gear 12 and to the output shaft 20.

In one embodiment the method comprises the steps of

a) using a clutch device 106 to ensure that the combustion engine isdisconnected,

b) disconnecting rotatable components 28, 32, 51 of the second planetarygear 12 from one another,

c) connecting a gear pair G1, 60, 72, which is connected to the firstplanetary gear 10,

d) disconnecting a gear pair G2, 66, 78, which is connected to thesecond planetary gear 12, and

e) connecting two rotatable components 28, 32, 51 of the secondplanetary gear 12 to one another.

Advantageously, the combustion engine is disconnected from the gearboxby the clutch device 106 situated between an output shaft 97 of theengine and the input shaft 8 of the gearbox.

Advantageously, the rotatable components 28, 32, 51 of the secondplanetary gear 12 comprise a second planet wheel carrier 51 and a secondsunwheel 32, which are disconnected at step b) by the two electricalmachines being operated in such a way that torque balance occurs in thesecond planetary gear 12. Thereafter a second clutch unit 58 is moved sothat the second planet wheel carrier 51 and the second sunwheel 32 aredisconnected from one another.

Advantageously, the gear pair G1, 60, 72 connected to the firstplanetary gear 10 is connected at step c) by the first electricalmachine 14 being operated in such a way that a synchronous speed isreached between a countershaft 18 and the gear pair G1, 60, 72 connectedto the first planetary gear 10, which gear pair is thereafter connectedto the countershaft 18.

Advantageously, the gear pair G2, 66, 78 connected to the secondplanetary gear 12 is disconnected at step d) by the two electricalmachines 14, 16 being operated in such a way that a torque-free stateoccurs between the countershaft 18 and the gear pair G2, 66, 78, whichgear pair is thereafter disconnected from the countershaft 18.

Advantageously, the rotatable components 28, 32, 51 of the secondplanetary gear 12 comprise a second planet wheel carrier 51 and a secondsunwheel 32 which are connected together at step e) by the secondelectrical machine 16 being operated in such a way that a synchronousspeed is reached between the second planet wheel carrier 51 and thesecond sunwheel 32, followed by their being connected together by thesecond clutch unit 58.

In another embodiment, the method also comprises in addition to theabove steps a)-e) the steps of

f) disconnecting rotatable components 22, 26, 50 of the first planetarygear 10 from one another,

g) connecting a gear pair G2, 66, 78, which is connected to the secondplanetary gear 12,

h) disconnecting a gear pair G1, 60, 72, which is connected to the firstplanetary gear 10, and

i) connecting two rotatable components 22, 26, 50 of the first planetarygear 10 to one another.

Advantageously, the two rotatable components 22, 26, 50 of the firstplanetary gear 10 comprise a first sunwheel 26 and a first planet wheelcarrier 50, which are disconnected at step f) by the two electricalmachines being operated in such a way that torque balance occurs in thefirst planetary gear 10. Thereafter a first clutch unit 56 is moved sothat the first planet wheel carrier 50 and the first sunwheel 26 aredisconnected from one another.

Advantageously, the gear pair G2, 66, 78 connected to the secondplanetary gear 12 is connected at step g) by the second electricalmachine 16 being operated in such a way that a synchronous speed isreached between the countershaft 18 and the gear pair G2, 66, 78, whichgear pair is thereafter connected to the countershaft 18.

Advantageously, the gear pair G1, 60, 72 connected to the firstplanetary gear 10 is disconnected at step h) by the two electricalmachines being operated in such a way that a torque-free state occursbetween the countershaft 18 and the gear pair G1, 60, 72, which gearpair is thereafter disconnected from the countershaft 18.

Advantageously, the two rotatable components 22, 26, 50 of the firstplanetary gear 10 comprise a first sunwheel 26 and a first planet wheelcarrier 50 which are connected together at step i) by the firstelectrical machine 14 being operated in such a way that a synchronousspeed is reached between the first planet wheel carrier 50 and the firstsunwheel 26, which are thereafter connected together by the first clutchunit 58.

In a further embodiment, the method also comprises in addition to theabove steps a)-e) the steps of

j) repeating step b),

k) connecting a gear pair G2, 66, 78, which is connected to the secondplanetary gear 12,

l) disconnecting a gear pair G1, 60, 72, which is connected to the firstplanetary gear 10,

m) using a clutch mechanism 96 to connect the first planetary gear 10 tothe output shaft 20,

n) repeating step d),

o) disconnecting a gear pair G3, 21 situated between the countershaft 18and the output shaft 20, and

p) repeating step e).

Advantageously, the gear pair G2, 66, 78 connected to the secondplanetary gear 12 is connected at step k) by the second electricalmachine 16 being operated in such a way that a synchronous speed isreached between the countershaft 18 and the gear pair G2, 66, 78, whichgear pair is thereafter connected to the countershaft 18.

Advantageously, the gear pair G1, 60, 72 connected to the firstplanetary gear 10 is disconnected at step l) by the two electricalmachines 14, 16 being operated in such a way that a torque-free stateoccurs between the countershaft 18 and the gear pair G1, 60, 72, whichgear pair is thereafter disconnected from the countershaft 18.

Advantageously, the first planetary gear 10 is connected to the outputshaft 20 at step m) by the first electrical machine 14 being operated insuch a way that a synchronous speed is reached between the output shaft20 and a first mainshaft 34, which is connected to the first planetarygear 10, followed by the clutch mechanism 96 being used to connect thesetwo shafts together.

Advantageously, the gear pair 3G, 21 situated between the countershaft18 and the output shaft 20 is disconnected at step o) by the secondelectrical machine 16 is operated in such a way that a torque-free stateoccurs between the countershaft 18 and the gear pair G3, 21 situated onthe output shaft 20, which gear pair is thereafter disconnected from thecountershaft 18.

FIG. 5 is a flowchart of a method for controlling a hybrid powertrain 3during electric drive. The hybrid powertrain comprises a combustionengine 4 and a gearbox 2, which is provided with an input shaft 8 and anoutput shaft 20; a first planetary gear 10 connected to the input shaft8; a second planetary gear 12 connected to the first planetary gear 10;a first electrical machine 14 connected to the first planetary gear 10;a second electrical machine 16 connected to the second planetary gear12; at least one gear pair G1, 60, 72 connected to the first planetarygear 10 and to the output shaft 20, and at least one gear pair G2, 66,78 connected to the second planetary gear 12 and to the output shaft 20.

The method comprises the steps of

a) using a clutch device 106 to ensure that the combustion engine isdisconnected,

f) disconnecting rotatable components 22, 26, 50 of the first planetarygear 10 from one another,

g) connecting a gear pair G2, 66, 78, which is connected to the secondplanetary gear 12,

h) disconnecting a gear pair G1, 60, 72, which is connected to the firstplanetary gear 10, and

i) connecting two rotatable components 22, 26, 50 of the first planetarygear 10 to one another.

Advantageously, the two rotatable components 22, 26, 50 of the firstplanetary gear 10 comprise a first sunwheel 26 and a first planet wheelcarrier 50 which are disconnected at step f) by the two electricalmachines being operated in such a way that torque balance occurs in thefirst planetary gear 10. Thereafter a first clutch unit 56 is moved sothat the first planet wheel carrier 50 and the first sunwheel 26 aredisconnected from one another.

Advantageously, the gear pair G2, 66, 78 connected to the secondplanetary gear 12 is connected at step g) by the second electricalmachine 16 being operated in such a way that a synchronous speed isreached between the countershaft 18 and the gear pair G2, 66, 78, whichgear pair is thereafter connected to the countershaft 18.

Advantageously, the gear pair G1, 60, 72 connected to the firstplanetary gear 10 is disconnected at step h) by the two electricalmachines 14, 16 being operated in such a way that a torque-free stateoccurs between the countershaft 18 and the gear pair G1, 60, 72, whichgear pair is thereafter disconnected from the countershaft 18.

Advantageously, the two rotatable components 22, 26, 50 of the firstplanetary gear 10 comprise a first sunwheel 26 and a first planet wheelcarrier 50 which are connected together at step i) by the firstelectrical machine 14 being operated in such a way that a synchronousspeed is reached between the first planet wheel carrier 50 and the firstsunwheel 26, which are thereafter connected together by the first clutchunit 58.

According to the invention, a computer program P is stored in thecontrol unit 48 and/or the computer 53 and which may comprise routinesfor controlling the hybrid powertrain 3 according to the presentinvention.

The program P may be stored in an executable form or in compressed formin a memory M and/or in a read/write memory.

The invention relates also to a computer program product comprising aprogram code stored on a computer-readable medium for conducting theabove method steps when said program code is run on the control unit 48or another computer 53 connected to the control unit 48. The programcode may be stored in a non-volatile way on said medium which can beread by a computer 53.

Cited components and features cited above may within the scope of theinvention be combined between different versions cited.

What is claimed is:
 1. A hybrid powertrain comprising: a combustionengine and a gearbox with an input shaft and an output shaft; a firstplanetary gear connected to the input shaft and a first mainshaft; asecond planetary gear connected to the first planetary gear and a secondmainshaft; a first electrical machine connected to the first planetarygear; a second electrical machine connected to the second planetarygear; at least one gear pair connected to the first planetary gear andto the output shaft; and at least another gear pair connected to thesecond planetary gear and to the output shaft; and a clutch deviceprovided between the combustion engine and the gearbox so that theengine can be disconnected from the gearbox, wherein a second planetwheel carrier of the second planetary gear is connected to the secondmainshaft, and wherein the input shaft is connected to a first planetwheel carrier of the first planetary gear.
 2. A hybrid powertrainaccording to claim 1, wherein the clutch device is situated between anoutput shaft of the combustion engine and the input shaft of thegearbox.
 3. A hybrid powertrain according to claim 1, wherein acountershaft is provided between the respective first and secondplanetary gears and the output shaft.
 4. A hybrid powertrain accordingto claim 3, wherein the at least one gear pair connected to the firstplanetary gear and the at least another gear pair connected to thesecond planetary gear are also connected to the countershaft.
 5. Ahybrid powertrain according to claim 1, wherein the first planet wheelcarrier of the first planetary gear is connected to a second sunwheel ofthe second planetary gear, and wherein a first sunwheel of the firstplanetary gear is connected to the first mainshaft.
 6. A hybridpowertrain according to claim 1, wherein a clutch mechanism is providedbetween the first mainshaft and the output shaft.
 7. A hybrid powertrainaccording to claim 1, wherein the countershaft is connected to theoutput shaft via a fifth gear pair.
 8. A hybrid powertrain according toclaim 1, wherein a first rotor of the first electrical machine isconnected to a first ring gear of the first planetary gear, and that asecond rotor of the second electrical machine is connected to a secondring gear of the second planetary gear.
 9. A hybrid powertrain accordingto claim 5, wherein a first clutch unit is arranged to connect the firstsunwheel releasably to the first planet wheel carrier, and a secondclutch unit is arranged to connect the second sunwheel releasably to thesecond planet wheel carrier.
 10. A vehicle comprising: an engine and ahybrid powertrain according to claim
 1. 11. A method for controlling ahybrid powertrain for effecting gear changes without torque brakes, thehybrid powertrain comprising a combustion engine; a gearbox having aninput shaft, an output shaft, a first planetary gear connected to theinput shaft and a first mainshaft; a second planetary gear connected tothe first planetary gear and a second mainshaft; a first electricalmachine connected to the first planetary gear; a second electricalmachine connected to the second planetary gear; at least one gear pairconnected to the first planetary gear and to the output shaft; at leastanother gear pair situated between and connected to the second planetarygear and to the output shaft; wherein a second planet wheel carrier ofthe second planetary gear is connected to the second mainshaft andwherein the input shaft is connected to a first planet wheel carrier ofthe first planetary gear, the method comprising: a) operating a clutchdevice to disconnect the combustion engine, f) disconnecting rotatablecomponents, of the first planetary gear from one another, g) connectingthe at least another gear pair, which is connected to the secondplanetary gear, h) disconnecting the at least one gear pair which isconnected to the first planetary gear, and I) connecting two rotatablecomponents of the first planetary gear to one another.
 12. A methodaccording to claim 11, wherein, at step f), the two rotatable componentsof the first planetary gear comprise a first sunwheel and a first planetwheel carrier, and further comprising operating the first electricalmachine and/or the second electrical machine to balance a torque in thefirst planetary gear, and then moving a first clutch unit to disconnectthe first planet wheel carrier and the first sunwheel from one another.13. A method according claim 11, wherein, at step i), the two rotatablecomponents of the first planetary gear comprise a first sunwheel and afirst planet wheel carrier, and further comprising operating the firstelectrical machine to reach a synchronous speed between the first planetwheel carrier and the first sunwheel, and then connecting the firstplanet wheel carrier and the first sunwheel together by the first clutchunit.
 14. A method according to claim 11, further comprising, at stepg), operating the second electrical machine to reach a synchronous speedbetween a countershaft and the at least another gear pair which isconnected to the second planetary gear, and then connecting the at leastanother gear pair connected to the second planetary gear to thecountershaft.
 15. A method according to claim 11, further comprising, atstep h), operating the first electrical machine to cause a torque-freestate between the countershaft and the at least one gear pair which isconnected to the first planetary gear, and then disconnecting the atleast one gear pair connected to the first planetary gear from thecountershaft.